Nanocatalysts for Electrocatalytic Oxidation of Ethanol

Abstract

The use of ethanol as a fuel in direct alcohol fuel cells depends not only on its ease of production from renewable sources, but also on overcoming the challenges of storage and transportation. In an ethanol‐based fuel cell, highly active electrocatalysts are required to break the C−C bond in ethanol for its complete oxidation at lower overpotentials, with the aim of increasing the cell performance, ethanol conversion rates, and fuel efficiency. In recent decades, the development of wet‐chemistry methods has stimulated research into catalyst design, reactivity tailoring, and mechanistic investigations, and thus, created great opportunities to achieve efficient oxidation of ethanol. In this Minireview, the nanomaterials tested as electrocatalysts for the ethanol oxidation reaction in acid or alkaline environments are summarized. The focus is mainly on nanomaterials synthesized by using wet‐chemistry methods, with particular attention on the relationship between the chemical and physical characteristics of the catalysts, for example, catalyst composition, morphology, structure, degree of alloying, presence of oxides or supports, and their activity for ethanol electro‐oxidation. As potential alternatives to noble metals, non‐noble‐metal catalysts for ethanol oxidation are also briefly reviewed. Insights into further enhancing the catalytic performance through the design of efficient electrocatalysts are also provided.

Recent Achievements in Noble Metal Catalysts with Unique Nanostructures for Liquid Fuel Cells

“…In addition„ the poor stability of commercial Pt/C catalysts is caused mainly by their unsatisfactory contact with the carbon support and spontaneous aggregation driven by surface‐energy minimization during the electro‐oxidation reaction . In addition, the carbon monoxide (CO)‐like intermediates formed in the alcohol oxidation reactions are absorbed on the catalyst surface, strongly affecting the long‐term performance and stability of these catalysts . Hence, the design and fabrication of highly efficient catalysts with satisfactory activity and stability are urgently needed for the further development of LFCs.…”

“…For example, Guo et al. surveyed the studies on nanowires and nanotubes for efficient fuel cell electrocatalysts, but focused only on Pt‐based catalysts, Chen and co‐workers discussed different catalysts for ethanol electro‐oxidation, and the review by Wang et al. focused on the synthesis and application of multimetallic nanosheets .…”

Ethanol Electrooxidation at Platinum-Rare Earth (RE = Ce, Sm, Ho, Dy) Binary Alloys

“…SnO 2 provides OH species to oxidize adsorbed residues and enhances the formation of acetaldehyde and acetic acid. On the other hand, the addition of Rh further increases the EOR activity and stability by promoting the C-C bond cleavage, thus improving the electrocatalytic performance in DEFCs [29,[75][76][77]. In this context, Adzic's group showed by in situ infrared reflection-absorption spectroscopy (IRRAS) that the integrated band intensities of CO 2 (2343 cm −1 ), CH 3 CHO (933 cm −1 ), and CH 3 COOH (1280 cm −1 ) for both Pt-Rh-SnO 2 /C and Pt-SnO 2 /C samples proved the enhanced cleavage of the C-C bond in ethanol and all three constituents Pt, Rh, and SnO 2 are needed to gain the synergistic effect in facilitating the total oxidation of ethanol [78].…”

Topological Type‐II Dirac Semimetal and Superconductor PdTe2 for Ethanol Electrooxidation

“…[1] It needs 12 electrons transfer to achieve the complete oxidation of ethanol in the electrocatalytic ethanol oxidation reaction (EOR), an essential reaction at the anode in DEFCs. [2,3] Electrocatalysts for EOR exhibit sufficient activity and enough durability. Extensive studies have demonstrated that Pd-based materials are excellent electrocatalysts for EOR.…”

“…[6,26,27] PdTe 2 nanosheets show a higher ECSA value (43.2 m 2 g À1 Pd ) than that of Pd black (16.6 m 2 g À1 Pd ) at the positive inversion potential of 1.33 V vs RHE. Taking into account that full utilization of Pd would be 448 m 2 g À1 , the Pd In general, there are two major pathways for the ethanol oxidation process [30] CH 3…”